Hurtado Daniel E, Villarroel Nicolás, Andrade Carlos, Retamal Jaime, Bugedo Guillermo, Bruhn Alejandro
Department of Structural and Geotechnical Engineering, School of Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile.
Institute for Biological and Medical Engineering, Schools of Engineering, Medicine and Biological Sciences, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, Santiago, Chile.
Biomech Model Mechanobiol. 2017 Aug;16(4):1413-1423. doi: 10.1007/s10237-017-0895-5. Epub 2017 Mar 18.
Understanding regional deformation in the lung has long attracted the medical community, as parenchymal deformation plays a key role in respiratory physiology. Recent advances in image registration make it possible to noninvasively study regional deformation, showing that volumetric deformation in healthy lungs follows complex spatial patterns not necessarily shared by all subjects, and that deformation can be highly anisotropic. In this work, we systematically study the regional deformation in the lungs of eleven human subjects by means of in vivo image-based biomechanical analysis. Regional deformation is quantified in terms of 3D maps of the invariants of the right stretch tensor, which are related to regional changes in length, surface and volume. Based on the histograms of individual lungs, we show that log-normal distributions adequately represent the frequency distribution of deformation invariants in the lung, which naturally motivates the normalization of the invariant fields in terms of the log-normal score. Normalized maps of deformation invariants allow for a direct intersubject comparison, as they display spatial patterns of deformation in a range that is common to all subjects. For the population studied, we find that lungs in supine position display a marked gradient along the gravitational direction not only for volumetric but also for length and surface regional deformation, highlighting the role of gravity in the regional deformation of normal lungs under spontaneous breathing.
长期以来，了解肺部的局部变形一直吸引着医学界，因为实质变形在呼吸生理学中起着关键作用。图像配准技术的最新进展使得无创研究局部变形成为可能，研究表明，健康肺部的体积变形遵循复杂的空间模式，并非所有受试者都有相同模式，而且变形可能具有高度各向异性。在这项工作中，我们通过基于体内图像的生物力学分析系统地研究了11名人类受试者肺部的局部变形。局部变形通过右拉伸张量不变量的三维图进行量化，这些不变量与长度、表面积和体积的局部变化有关。基于个体肺部的直方图，我们表明对数正态分布能够充分代表肺部变形不变量的频率分布，这自然促使我们根据对数正态分数对不变量场进行归一化。变形不变量的归一化图允许直接进行受试者间比较，因为它们展示了所有受试者共有的变形空间模式。对于所研究的人群，我们发现仰卧位时肺部不仅在体积上，而且在长度和表面积局部变形方面都沿重力方向呈现明显梯度，突出了重力在自主呼吸下正常肺部局部变形中的作用。
